Golden-cheeked Woodpecker—spotted in Mexico

 

We saw several Golden-cheeked Woodpeckers (Melanerpes chrysogenys) while we were in Mexico in February. This one is a male and was photographed near San Blas.

Like the Black-throated Magpie-Jay we also saw in the same part of western Mexico, it was named by Nicholas Vigors from a specimen collected by the expedition led by Frederick William Beechey (1796-1856) on board HMS Blossom. I have no doubt their bird was shot during the ship’s short stay in San Blas in December 1827.

A Mexico endemic, the Golden-cheeked Woodpecker occurs in woodland on the Pacific side of the country. Considered common and widespread within its range, it was greeted with delight as a ‘cracking woodpecker’.

Vigors NA, 1839. Ornithology. pp. 13–40. In: Richardson J, Vigors NA, Lay GT, Bennett ET, Owen R, Gray JE, Buckland W,  Sowerby GB. The Zoology of Captain Beechey’s Voyage; compiled from the collections and notes made by Captain Beechey, the officers and naturalist of the expedition, during a voyage to the Pacific and Behring’s Straits performed in His Majesty’s Ship Blossom, under the command of Captain F.W. Beechey, R.N., F.R.S. &c &c in the years 1825, 26, 27 and 28: i–xii, 1–180. London.

Snakes, Drugs and Rock ’N’ Roll. My Early Years. Romulus Whitaker with Janaki Lenin. HarperCollins, India. 2024

 

I first heard of Rom Whitaker in the late 1970s. He was in process of becoming established as the mover and shaker in the study and conservation of reptiles in India. This book is a frank account of his early life and of how, born in New York in 1943, he first went with his family to India where he was schooled, returned to the USA as a snake-mad youth, served in the US Army as a medical lab technician, sailed the world as a merchant seaman to make money (of which he was always short) and then moved back to India.

The title of the book, Snakes, Drugs and Rock ’n’ Roll. My Early Years, saves everything you need to know about the book before pressing the ‘buy now’ button. Importantly, it describes the exploits of reptile-mad young men and women in the light of what constituted amateur and commercial herpetology in the USA in the decades towards the latter half of the 20th century.

Black-throated Magpie-Jay in Mexico—Surgeon Collie’s Bird of HMS Blossom

 

We spotted this Black-throated Magpie-Jay (Cyanocorax colliei) in the late afternoon in Puerto Vallarta on the Pacific Coast of Mexico in February. It was one of a small group that sat long enough for a photograph. I had to pinch myself in order to remind me which continent I was on since this bird resembles in flight, jizz and general coloration the Red-billed Blue Magpie (Urocissa erythroryncha) found in Hong Kong. It was good that we also saw this species further up the coast near the town of San Blas from where the original specimen was sent to London.

Alexander Collie

Educated in Edinburgh and London, a Fellow of the Royal College of Surgeons, Alexander Collie (1793-1835) was the ship’s surgeon on board HMS Blossom, a ship specially fitted out for exploration of arctic waters. Blossom (1806-1848) was commanded by Frederick William Beechey (1796-1856), a future rear-admiral, Fellow of the Royal Society and President of the Royal Geographical Society. His job was to explore the north-west Pacific, particularly the Bering Strait, in the hope of finding a Northwest Passage to the Atlantic. The famous expedition took nearly three years from 1825. The naturalist on board was not Collie, as I have seen stated, but George Tradescant Lay (c1800-1845).

HMS Blossom reached San Blas, 100 miles north of Puerto Vallarta, on the way back from the north on 20 December 1827. I have read that ships of the Royal Navy often used San Blas as a victualling stop when operating in the eastern Pacific.

Nicholas Vigors

Back in London, Nicholas Aylward Vigors (1785-1840) described the ornithological results in a chapter for the zoological account of the expedition. There were several ‘new’ species. This spectacular corvid named for Collie was one of them. Beechey was not left out; the  Purplish-backed Jay (now Cyanocorax beecheii) from the same part of Mexico was named for him. Vigors, the first Secretary of the newly established Zoological Society of London was at the time also heavily involved in the opening and early growth of London Zoo, the formation of a museum for the Society, as well as a practising barrister. The offices, library and museum were at 33 Bruton Street.

Vigors published preliminary account of the birds from Beechey’s expedition in the Zoological Journal in 1829:

Frederick William Beechey

Captain Beechey, on his return from the late expedition to the Western shores of North America, having kindly transmitted to me the publick collection of birds formed during that expedition, for the purpose of making a catalogue of them for the Appendix to the forthcoming account of his voyage, and several other species also from the same locality, but not existing in the publick collection, having been presented to the Zoological Society from various quarters, I have had the pleasing opportunity of observing among them many species which are rarely found in our home collections, as well as a few which appear altogether new to science. Being aware of the advantages arising from the speedy publication of such recent acquisitions, and presuming that some time must elapse before the Account of the Voyage will appear, I have requested and obtained Captain Beechey's permission to give a brief account of a few of the more interesting species in our Journal, previously to their appearing more at large in the Appendix to his work. In this undertaking I shall confine myself merely to the technical description of the birds. The more valuable part of the account of them will be reserved for the more detailed work; in which I may here venture to promise much interesting information, extracted from the journal of Mr. Collie, Surgeon, and Mr. Tradescant Lay, Naturalist, to the expedition. The notes of these gentlemen not only furnish us with the habits and localities of the birds which have been brought home, but also with what is rarely attended to by collectors abroad, an account of their internal structure.

There follows the description of the two new species. Here is Mr Collie’s bird:

PICA COLLIEL.

Pica macula subrictali, corporeque suprà caruleis; fronte, cristá, genis, colloque inferiore nigris; corpore subtus, rectricumque externarum apicibus albis, caudú elongatissimá.

Crista erecta, elongata, antrorsum spectans, facies pectusque intensê nigra. Supercilia, colli latera, pectusque medium albo notata. Tectrices inferiores alba. Rectrices quatuor media suprà carulea, subtùs nigrae. Longitudo corporis ab apice rostri ad apicem cauda, 2 Ped., 4 Unc.; rostri, 1 7/10 ; ale a carpo ad remigem 5tam, 8; cauda ad apicem rectricis media, 19½; externa, 6 ; tarsi, 2.

This beautiful species, which was met with at San Blas, was not in the publick collection sent to me by Captain Beechey. The specimen from which the above description was taken, was presented to the Zoological Society by A. Collie, Esq., Surgeon to the Blossom, to whose exertions, during the expedition, natural science owes many important obligations. To him I beg leave to dedicate the species.

HMS Blossom leaving Spithead 19 May 1825

Fort San Basilio, San Blas
Built in 1760, the fort overlooks the whole area of San Blas and the sea

Vigors NA. 1829. On some species of birds from the north-west coast of America. Zoological Journal 4, 352-358.

‘Perpetuating a mischief’: Sharpey-Schafer’s Classic Histology Textbook Displaced by Evelyn Hewer’s

It is 1959. The two of us starting ‘A’ level Zoology that year really thought we had had started playing with the big boys. Instead of the elementary textbooks used for ‘A’ level Biology we had access to the very few more advanced book kept in a glass-fronted cupboard in the biology library. One of the books was Essentials of Histology by Sir Edward Sharpey-Schafer. I cannot remember which edition it was which is not surprising when, after the first in 1885, it had reached 14 by 1938 and, finally, 16 by 1954, nearly 20 years after the death of the original author. Sharpey-Schafer was for decades the histology text in British universities. Thus It came as something as a shock on reaching university that the recommended textbook was not Sharpey-Schafer but Histology for Medical Students by Evelyn E. Hewer which was, in October 1962, in its 7th edition and shortly to reach its 8th. That shock was amplified by finding the histology course was held on Saturday mornings.

An illustration from Sharpey-Schafer (5th Edition, 1898)
It is interesting to note that although the myopithelial cells had already been described by German
histologists, later shown to be responsible for milk ejection, Schafer made no mention of them

From Hills Biographical Memoir of Sharpey-Schafer

The American 5th Edition  available
online at Internet Archive

Microscopy with its attendant techniques for histology and cytology involving reagents and equipment with exotic-sounding  and esoteric names were central to zoology as well as to the medical sciences. Few labs were without the equipment necessary to produce microscope slides of whatever organism, organ, tissue or cell was being studied. Mammalian histology for medical and medical science students was though taught then and somewhat anomalously by physiology departments, following the precepts of Sharpey-Schafer himself who was a physiologist.

Schafer held strongly to the view that histology should be part of physiological teaching and deplored the modern tendency to relegate it to the anatomist. Up to Sharpey’s time Anatomy had been considered to be the foundation of medicine and surgery; the young Schafer pointed out that this was only justifiable if the object of medical education were to provide physicians, not for the living, but for the dead, and in 1885 he published Essentials of Histology, a book aimed at supplying students with data necessary for understanding physiological functions.

Jumping to ten years or so later, the coffee room conversation had turned to some point of histology that needed to be looked up. Heading for the door into the corridor, JLL, in his usual stentorian voice said, ‘I’ll get my copy of Schafer’. That announcement was met by a boom and a plume of cigar smoke from the cell-like office across the corridor. Its occupant, Amo, shouted, ‘You’ll be perpetuating a mischief if you do!’ Amo then appeared through the fug to extol the virtues of Hewer over Sharpey-Schafer. I went off to get my copy but neither volume provided the information we were looking for.

I was reminded of this rivalry between two textbooks when writing about William Rowan and the control of reproduction and migration by daylength, since it is Sharpey-Schafer who came up with the idea in the early years of the 20th century. The insight also reveals the breadth of Schafer’s knowledge, interest and leadership far beyond the narrow approach that became manifest in the physiology departments of some medical schools. Preceding generations also simply referred to Sir Edward Sharpey-Schafer as Schafer because that was his original name. He was born Edward Albert Schäfer in London, the son of German immigrant who became naturalized and a British mother. As a medical student at University College London Schafer was greatly influenced by William Sharpey (1802-1880)  who was professor of anatomy and physiology. Later, Schafer became the first Sharpey Scholar in 1873. Both of Schafer’s  sons were killed in the First World War, one had as one of his names, Sharpey. In order to commemorate Sharpey and his sons, Schafer took the surname Sharpey-Schafer in 1918.

The later editions of Essentials of Histology were revised mainly by Harry Montgomerie Carleton (1896-1956) who taught histology and histological techniques at Oxford—in the Sharpey-Schafer tradition in the physiology department.

A battered copy of the last edition
revised by Evelyn Hewer

Compared with 1885, Hewer’s Histology for Medical Students was the newcomer to the textbook market. with the first edition appearing in 1937. The final (9th edition) was published in 1969 but Hewer dropped out of the further revisions after the 5th when she retired. Evelyn Everard Hewer (1889-1975) was Reader in Histology in the University of London and first Demonstrator, then Assistant Lecturer and then Lecturer in Physiology at the Royal Free Hospital Medical School in London. She was born in north London on 4 June 1889, the daughter of Joseph Langton Hewer, a general practitioner with an MD degree, and his wife, Annie Martha, a writer (Our Baby: For Mothers and Nurses, Antiseptics: a Handbook for Nurses,  and reviewer). She educated at the North London Collegiate School for Girls and entered Bedford College for Women in 1908. She listed the subjects of her first degree: Maths, Chemistry and Zoology, and graduated in 2010. The honours course was another year and she graduated with first-class honours in physiology in 1911. In 1909 she had been listed as a medical student at Bedford College but clearly went down the science rather than the medical degree route. She was then awarded a University Studentship for research (£50 for the year) and obtained an MSc, the highest degree available at the time, in 1916. In the days before the PhD she was awarded the higher doctorate (probably on the basis of publications and, possibly in London University, a thesis) in science in 1922.

By the time of the 1921 census Evelyn Hewer was lecturing in the physiology department of the Royal Free Hospital School of Medicine for Women; there she stayed for the rest of her career, at some stage being appointed Lecturer and then Reader in Histology by the University of London. It was then possible to be a Reader in the university but a Lecturer in a constituent college. The various censuses and electoral registers from the early decades of the last century show her living with her parents in Highbury, London (1911), St Albans (1921), Finchley Road, London (1929) and Lyndale Avenue, London (1930, 1934). However, in 1919 she was living on her own in a flat in Hammersmith.

Her only appearance in the newspapers to which I have access concerned her research studentship and an accident in July 1915 (Western Times 29 July) in which the car she was driving  with her sister as passenger collided with another in South Molton, Devon. A virtually identical collision had occurred at the same spot as another four days earlier. Both front wheels ‘were broken clean off’. ‘There were other injuries of a minor character’.

Evelyn Hewer published on a variety of topics, generally concerned with human early embryonic development and the physiological events of pregnancy. She was also co-author of a book on the nervous system in 1929. One of her papers (with Mary Frances Lucas Keene (1885 –1977), professor of anatomy at the Royal Free and the first female professor of anatomy in the UK), was a classic and of particular interest to me.  They were the first to describe the separate origins of the human fetal adrenocortical tissue and the adrenal cortex of the adult.

Evelyn Hewer died on 2 December 1975. Her address was given as 3 Hamp Green Rise, Bridgwater, Somerset; she was 86.

Both textbooks must have very profitable for their publishers. I suspect that both were run on beyond their sell-by-dates, for 69 and 32 years. Revising textbooks is an increasingly difficult job with the passage of time and the point comes when a fresh approach is needed. I cannot remember why Amo thought Sharpey-Schafer’s book, at least in its later editions, was ‘perpetuating a mischief’. 

Hill, LE. 1935. Sir Edward Albert Sharpey-Schafer, 1850-1935. Biographical Memoirs of Fellows of the Royal Society 1, 401-407 doi: 10.1098/rsbm.1935.0005

Lucas Keene MFL, Hewer, EE. 1927. Observations on the development of the human suprarenal gland. Journal of Anatomy 61, 302-324

Citreoline Trogon: a bird endemic to western Mexico

Citreoline Trogon
1 February 2025, El Jorullo, Jalisco, Mexico

We saw this Citreoline Trogon after walking across the 470 metre long suspension bridge at El Jorullo a few miles inland from Puerto Vallarta on the Pacific Coast of Mexico. We had to wait for a while because Canopy River park is used for all sorts of outdoor activities and several convoys of all-terrain vehicles were heading in the opposite direction. The suitability for such vehicles makes it, so it is claimed, the longest vehicular suspension bridge in the world. The whole area has been owned and operated since 1940 by an association of local foresters; the vehicles and zip wire etc came later, after 2005. The Sierra Madre mountains provide a backdrop to the protected area of forest while the Cuale River runs way below the bridge.

Jorullo Suspension Bridge

The Citreoline Trogon (Trogon citreolus) is endemic to the woods and forests of western Mexico. They nest by digging into the nests of tree termites. This one was eating berries and at various times of year eat either or both fruit and insects.

From the photograph at high magnification it can be seen that the trogon has two toes visible at the front. Does that make it a zygodactyl like parrots and woodpeckers? Well, no. It does have two toes at the front and two at the back but in trogons digits 3 and 4 face forward while 1 and 2 face back. In zygodactyly, 2 and 3 face forward and 1 and 4 back. Trogons are thus described as heterodactylous.

There were mammalian delights too along the trail through the forest beyond the suspension bridge but they are for later.

Comparative Endocrinology Revisited: Hellbenders, Giant Salamanders and their hormones

Hellbender from the Appalachian Mountains
Brian Gratwicke Creative Commons Attribution 2.0 Generic

In a recent article I mentioned that there is still discussion on why the adrenal glands of different groups and species of vertebrates produce either or both of the two steroid hormones, cortisol and corticosterone. Both are these hormones are glucocorticoids, originally named for their effect on glucose metabolism and both have wide-ranging effects on the body. Both have a little mineralocorticoid action, i.e. acting to retain sodium, the role of the other major adrenal steroid hormone, aldosterone. In different tissues of different animals corticosterone and cortisol have been found to have slight differences in their mineralocorticoid action.

The difference between corticosterone and cortisol is the absence or presence of a hydroxyl moiety at the 17 carbon position of the steroid molecule. Corticosterone does not have it; cortisol does. In some mammals, rats and mice for example, the adrenal cortex does not have the enzyme 17α-hydroxylase* An earlier chemical precursor of cortisol is therefore not produced, leaving corticosterone as the only glucocorticoid produced by the rat adrenal. Since aldosterone has been found in all vertebrates, corticosterone must also be produced since it is a precursor in aldosterone synthesis. In some animals that produce both corticosterone and cortisol, one or the other may predominate. In primates it is cortisol.

The structural difference between corticosterone and cortisol (ringed in red)
Adapted from the classic textbook by Aubrey Gorbman and Howard Bern,
A Textbook of Comparative Endocrinology, New York: John Wiley. 1962

A paper published in 2020 raised an interesting question and demolished the generally accepted view that corticosterone is the major and perhaps the only major glucocorticoid produced by the adrenal cortex of amphibians. Hellbenders (Cryptobranchus alleganiensis) are the American relatives of the Giant Salamanders of East Asia. They too are large, but not so large, up to 70 cm in length, long-lived and fully aquatic. As part of an extensive study of an amphibian in decline in the wild, the concentration of cortisol was found to be five times that of corticosterone in blood taken from a tail vein. The difference was even greater—up to ten times—after the injection of mammalian adrenocorticotrophic hormone (ACTH). The authors suggested that cortisol may predominate, as it does in fish, in these aquatic salamanders since in other vertebrates cortisol has a somewhat greater mineralocorticoid activity than corticosterone thereby preserving salt and water balance. However, that inference, at first sight, does not seem to hold. In work done in Hong Kong by my old fellow postgraduate student Samuel Chan, Tom Sandor (1924-2003) (a doyen of steroid biosynthesis in vertebrates) and Brian Lofts (1929-2015) only corticosterone was found after adrenal tissue from similarly aquatic Chinese giant salamanders (Andrias) was incubated with radiolabelled precursors in the steroidogenic pathway.

The authors of the papers on the Hellbender drew up a table showing previous studies on the occurrence of corticosterone and cortisol in amphibians and emphasised the difficulties of interpreting studies in which blood concentrations were recorded and experiments on adrenal tissue in vitro. They also noted that a number of studies were done before reliable methods had been established for identifying and quantifying corticosterone in the presence of cortisol and vice versa. They made sure that they established the chemical identity of the hormones using mass spectroscopy—something not possible in the early studies with the low but biologically active concentrations found in blood plasma. However, there is another difference that may be significant: the site from which blood was taken. Because the analytical methods did not exist at the time to study hormones in peripheral blood, John Phillips (1933-1987) made his name in the late 1950s by devising techniques to sample blood from the veins draining the adrenal gland or from those that carried a high proportion of adrenal venous effluent. The distinction is important because, as I suggest below, any production of adrenocortical-like hormones from elsewhere in the body would not have been at detectable concentrations.

What could be the explanation of the findings in the Hellbender and indeed in those amphibians in which both corticosterone and cortisol have been found to be present in the blood (albeit with the caveats on methodology outlined above)? I suggest there are two hypotheses which are not mutually exclusive:

1. The adrenal tissue expresses the gene CYP17A1 that produces 17α-hydroxylase during the breeding season but not at other times. The Hellbenders sampled were, as the authors note, caught in late summer ‘prior to nesting because at this time adult male and female hellbenders can be distinguished by the swollen cloaca of males’. There is evidence gathered in the first half of the twentieth century that the adrenal of many amphibians varies in appearance, both macroscopic and microscopic, according to season. In newts and salamanders the adrenals are multi-segmented strands of tissue on the ventral side of the kidneys. In the California Newt (Taricha torosa), as one example, during the two-month breeding season the adrenal is bright orange in colour and expanded compared wit the non-breeding season when the gland is dull, smaller and flatter. In other words, the gland waxes and wanes and it is easy to imagine that the production of 17α-hydroxylase follows a similar pattern. An adrenal with 17α-hydroxylase is also capable of producing androgens that might play a role in reproduction.
2. The adrenal is not the site of cortisol synthesis or secretion. The gonads in a number of vertebrates are known to be capable of synthesis and secretion of adrenocorticosteroids. Of necessity in being able to sythesise androgens and oestrogens they must express CYP17A1. The adrenal, testis and ovary are all of similar embryonic origin and complete separation of steroid synthesis and secretion   is far from complete with overt clumps of cells characteristic of the adrenal cortex being present in the ovary.

A possible clue as to the cellular origins of of the two adrenal steroids is that while in the Hellbender both corticosterone and cortisol concentrations increased in response to ACTH the time course was different and there was no correlation between concentrations of the two hormones in blood at any time point. Thus corticosterone reached a peak at one hour after ACTH; cortisol at three hours. Does this finding suggest a different cellular origin of the two steroids? I suspect that it does with either two cell populations in the adrenal itself (one only seasonally present producing cortisol and probably androgens, the ‘permanent’ cells producing corticosterone) or of the adrenal producing corticosterone and the ovary and testis producing cortisol as well as androgens and oestrogens.

Assuming that the other members of the cryptobranchid family have a similar endocrine system, both of these possibilities are compatible with the finding of cortisol and corticosterone in the blood of Hellbenders but the finding of only corticosterone  being produced in vitro by the adrenal of Chinese giant salamanders, assuming of course the latter were not in the breeding season or breeding condition.

Chinese Giant Salamander (Andrias sp)
On the roof of the now demolished Northcote Science Building
Univewrsity of Hong Kong ca 1966

I would argue that the next step in solving this problem lies in China where farm-bred Giant Salamanders are readily available in the restaurant trade. The question is a simple one: what are the concentrations of corticosterone and cortisol in the blood at different stages of the reproductive cycle? Modern students may prefer the question in molecular biological terms: where are the sites of expression of the gene CYP17A1?

...And surely the Axolotl is just asking to be looked at!

Comparative endocrinology may no longer be fashionable but there are still important areas where new knowledge and a look at unsolved old problems are needed if we are to understand how signalling systems that operate between organs and tissues work. The science of intercellular signalling is now being neglected. 

*I have seen the odd paper showing cortisol as present in mice (at least in a particular strain of lab mouse) but without comment as to the significance of the finding.

The paper on the Hellbender:

Hopkins WA, DuRant SE, Beck ML, Ray WK, Helm RF, Romero LM. 2020. Cortisol is the predominant glucocorticoid in the giant paedomorphic hellbender salamander (Cryptobranchus alleganiensis). General and Comparative Endocrinology 285, 113267 doi: 10.1016/j.ygcen.2019.113267

The paper on the Chinese Giant Salamander:

Chan STH, Sandor T, Lofts B, 1975. A histological, histochemical, and biochemical study of the adrenal tissue of the Chinese giant salamander (Andrias davidianus Blanchard). General and Comparative Endocrinology 25, 509–516 doi: 10.1016/0016-6480(75)90161-6

For the older literature on the adrenal gland of amphibians:

Chester Jones I. 1957. The Adrenal Cortex. Cambridge: Cambridge University Press.

UPDATED 17 JUNE 2025

Crocodiles and Birds at the Mirador de las Aves near San Blas in Mexico

We have seen lots of crocodilians in the wild but rarely doing anything but sunning themselves or just lying in the water. When we pulled into a lay-by complete with food stalls and an iron-railinged viewing area on the outskirts of San Blas in Mexico to look at the birds on the lagoon and in the surrounding mangroves, I had read that American Crocodiles (Crocodylus acutus) could be seen there. The lay-by whose name gives a clue as to its avian delights, Mirador de las Aves, is clearly a popular place to stop, buy a snack and look at the wildlife as locals drive along the road on a Sunday evening.

And there were crocodiles, large ones hauled out just under the viewing platform and basking in the sun on the edge of the lagoon. However, as the sun went down and moved off the crocodiles they entered the water and several apparently began searching the bottom for food with one, as the video below shows, emerging to swallow something small it had caught or found. Eventually I counted seven moving around offshore or simply hanging in the water as dusk fell.